The present invention relates to the art of interlocks, more particularly to electrostatic mechanical interlocks. The invention can be used in transmissions for development of valve-actuating mechanisms of gas/hydraulic distribution systems that make it possible to control the operation of said mechanisms and transmissions by low-power electrical signals.
The invention can be also used for development of electronic locks, electrical clutches and other transmission mechanisms, electronically controlled valve-actuating mechanisms and other interlocks characterized by very low energy consumption.
Known in the art is an electrostatic interlock (cf., U.S. Pat. No. 4,912,460), which uses the effect of electrostatic interaction of individual members in order to move them and set in different positions.
In the prior art interlock, the magnitude of electrostatic attraction forces between members of the electrostatic interlock essentially depends upon features of machining the surfaces of interacting members and upon a distance therebetween.
It is common knowledge that the electrostatic forces increase with an increase in the effective contact area of interacting surfaces, with a decrease in the effective distance therebetween, and with the growth of the dielectric permittivity of the spacing therebetween.
These conditions restrict the use of the prior art device, because the forces of electrostatic attraction of said interlock members spaced originally at a certain distance from one another will be very small to permit reliable control of their mutual approach. Besides, direct use of electrostatic forces for bringing together the electrostatic interlock members is uneconomical from the viewpoint of energy saving.
In another prior art device (RU Patent No. 2,042,028), electrostatic interaction of members is more effective, because the members are in close proximity to one another, and their mutual positions are retained by friction forces increasing indirectly under conditions of electrostatic interaction. Hence, the electrostatic forces not make any mechanical work and, therefore, not consume any additional energy from an electric energy source.
As indicated, however, the electrostatic interaction force used in both prior art devices depends upon roughness of surfaces, presence of foreign particles therebetween, and upon irregularity of the gap therebetween.
High requirements developed therewith to a degree of polishing of member surfaces, their mutual flatness or, generally, mutual conformity of interacting surfaces, and the requirements to a purity of member assembling make such the devices expensive, reduce operation reliability and service life, and limit applicability as well.
It is an object of the present invention to provide an electrostatic mechanical interlock and a method of manufacturing thereof that would be capable to provide inexpensive manufacture of the design of an electrostatic unit for location of members of electromechanical devices, and would be capable to provide reliable location of electrostatically interacting members.
The above object is accomplished in that, in an electrostatic unit for location of members of a mechanical device, which electrostatic unit comprises a locating member arranged in an electrostatic location unit housing that is movable from one position to another, an electrostatic location means designed for location of the locating member in one of the positions and being placed in the housing and comprising two electrically conductive members and a layer of a dielectric therebetween, conformal surfaces of the electrically conductive members being designed for electrostatic interaction and mutual location of one relative to the other when they are set in close proximity to each other and when an electric charge is applied to the electrically conductive members, one of said members of the electrostatic location means being kinematically linked to the locating member, a means for applying an electric charge to the electrically conductive members, said means being connected to the electrically conductive members, according to the invention, at least one member of the electrostatic location means comprises a layer of an elastic material on a conformal surface, and the elastic material is selected from the group consisting of an electrically conductive material and a dielectric material.
One of the principal advantages of using the elastic material is associated with that, in contacting the conformal surfaces of the electrically conductive members positioned in close proximity to one another, the elastic material clings irregularities of interacting surfaces associated with their roughness, point defects and, in particular, compensates for loose pressing the non-flat surfaces to each other. With this, the effective contact area of conformal surfaces increases, and their electrostatic interaction force increases respectively.
This advantage makes it possible to reduce operating electrical voltages necessary for reliable operation of the electrostatic location unit.
Another important advantage of using the elastic material reveals itself if said material is used in electrostatic units operating under conditions of elevated vibration when the effective distance between conformal surfaces is subjected to rapid change with a resultant weakening or even a momentary loss of electrostatic interaction of members. The use of the elastic material in the gap between the members also effectively compensates for such temporary variations in the size of the gap.
Yet another advantage of using the elastic material is that it allows for a coarser closing and setting of conformal surfaces into close proximity to one another, which sufficiently simplifies the process of manufacturing the interacting members and means for their setting.
Elastic materials required for accomplishment of the object of the invention may be dielectric or electrically conductive materials. In case if an elastic material is electrically conductive, it is advisable to arrange a non-elastic dielectric separating the conformal surfaces on the mating hard surface. Should a dielectric elastic material was selected, it is important that its thickness is sufficiently small and its dielectric permittivity is sufficiently high to provide effective electrostatic interaction of electrically conductive members separated thereby.
An elastic material may also be in a form of a multi-layered material comprising electrically conductive and dielectric sublayers. Such a form is suitable in those cases when the elasticity of a layer is provided by one of the sublayers, for instance, by a dielectric sublayer, while a second sublayer is made to be sufficiently thin and performs electrical conductance functions of the material or, conversely, an elastic layer is electrically conductive while the other thin sublayer performs dielectric functions.
Electrically conductive sublayers in an elastic material may be provided in different ways, for instance, by depositing a sublayer of a metal onto a sublayer of a dielectric material, introducing particles of an electrically conductive material into a surface region of the dielectric sublayer by diffusion or implantation, and also by chemical or stoichiometric methods for changing a composition of the surface region of the dielectric sublayer a result of which is electrical conductance.
Similar methods can be used to develop dielectric sublayers coating an electrically conductive sublayer, for instance, by depositing a dielectric sublayer, oxidizing a surface of the electrically conductive sublayer, and also by other chemical or electrochemical modifying the surface of the electrically conductive sublayer as a result of which the surface becomes dielectric.
Very moderate in price and the most easy in use is an elastic material produced as a thin elastic film secured on a carcass.
The film can also be produced as a multi-layered structure comprising electrically conductive and dielectric sublayers. The most preferable embodiment of an elastic film having a conducting sublayer is an elastic dielectric polymeric film having a thin layer of a metal deposited onto one or both surfaces.
The film may be attached to a respective member of the electrostatic location means by both fastening the carcass on said member and by direct attaching determined portions of the film to determined portions of the member.
In doing so, embodiments are allowable wherein a film is attached to a member of an electrostatic location means while a carcass has no link to said member and is held in the structure owing to film tension, as a result of which a freedom degree is added in the process of adapting a film surface of the member of the electrostatic location means to a conformal surface of another member.
An additional advantage of using thin elastic films consists in that different, generally three-dimensional topological forms can be given to a film surface by varying a form of a carcass. Thus, the carcass can have a contour in the form of a flat circle, a rectangle, or a complex three-dimensional contour.
In some cases, a carcass can be made of an elastic material and change its form under mechanical action thereto.
For securing of a film on a member of the unit and/or on a carcass one can use different processes, such as gluing, welding or clamping like a film in a tambour.
When it is necessary to isolate electrically conductive members and mechanical members of a unit galvanically, it is advisable to apply an electric charge directly to the electrically conductive sublayer of the film, for which purpose a means for applying an electric charge should be connected directly to the electrically conductive layer or sublayer of the film.
Many designs require to manufacture a multi-member carcass for the film, e.g. a carcass comprising multiply linked members.
For instance, a carcass consisting of two non-linked rings, a diameter of one ring being more than that of the other while the rings being arranged in one plane and one inside the other, allows to fasten the film as a flat ring. Such a carcass is necessary in devices where a mechanical axle should be placed to pass through an inner ring of the carcass. In doing so, it is permissible to fasten only one of the carcass rings on members of an electrostatic location means. Free position of the second ring provides optimum adaptation of conformal surfaces of interacting members to each other.
A carcass comprising two rings that have equal diameters, are placed in different parallel planes and have centers on the same axis, makes it possible to give a cylinder form to the elastic film. An embodiment of such a conformal surface of a member of an electrostatic location means permits to manufacture electrostatic location units of a small overall dimension in one direction for different compact electromechanical devices.
A carcass comprising a ring and a disc which have different diameters, are placed in different parallel planes and have centers on one axis, makes it possible to fasted the film as a cone. This design is preferable in case of small overall dimensions when it is necessary to move apart conformal surfaces to a certain distance from one another.
In a general case, the film may be fastened such that a part of a film contour may be free and have no fastening on the carcass. For instance, such an embodiment of an electrostatic location means is tolerable when a film of a rectangular contour form is fastened on a rigid carcass only along one or two sides. Then, additional freedom degrees occur for final forming a film surface, the additional freedom degrees allowing said surface to adapt to a form of its mating second electrically conductive member of an electrostatic location means, which member can have the form of a cylinder or the form of a thin bar, etc.
Since the distribution of the electric charge over the surface of the electrically conductive member is but little effected by the resistance of its layers, the elastic material can be selected from the group of electrically conductive polymeric materials whose conductance is not high in comparison with metals, but whose elastic properties of polymers are strongly pronounced.
When selecting a polymeric base for elastic materials, both bulk-high and film-thin, for their layers and sublayers as well as for coatings on non-elastic surfaces of electrostatically interacting members of an electrostatic location means, it is advisable to turn to materials having high mechanical wear resistance, high dielectric constant, climatic and temperature stability and longevity.
The above qualities are typical for materials based on or containing polyethylene terephtalate, polytetrafluoroethylene, polytrifluorochloro-ethylene, polyimide as well as different kinds of rubbers, in particular, silicon rubber.
A promising pair of materials for members of an electrostatic location means is a pair of an elastic conductive polymer on one member and a semiconductor material on another member. Besides all the aforesaid advantages of using an elastic material, this pair will display the effect of lonson-Rabek.
The design of the electrostatic location unit allows different variants of setting, mutual movement and final positions for conformal surfaces of unit members.
Conformal surfaces may be arranged in close proximity to one another, particularly, may be in complete or partial contact.
At the same time, mutual movement can take place along a conformal surface. Conformal surfaces can reciprocate and perform rotary motions, and when an electric charge is applied to electrically conductive members, the location of mutual position will take place owing to an indirect increase of friction forces.
In another embodiment of the electrostatic location unit, conformal surfaces of electrically conductive members may have two extreme positions: in close proximity to one another and at a certain distance from one another; hence, said members can move both along a conformal surface and along a normal thereto.
In a position when surfaces of said members are spaced, their possible electrostatic interaction weakens considerably, therefore, mutual location of position of members is possible only if they are set in close proximity. Such a setting may be achieved by exerting a certain influence to the locating member kinematically linked to one of said members.
In most designs, mutual position of electrically conductive members has one initial position, and there is a need for additional setting a means for returning electrically conductive members to this position after they have completed their mutual movements. Such a means may be directly linked to electrostatically interacting members or, as a possible alternative, link the locating member and the housing of the electrostatic location unit.
A wide way to introduce electrostatic location units is their use as electromechanical gate control mechanisms for gas/hydraulic distribution systems.
Assigned to such units is an electrostatic location unit made as an electromechanical valve, said unit further comprising a pipe with a valve seat and a gate for a hole of this seat, which gate is capable to take two positions: in one position, the hole of the seat is closed, and in the other position, the hole of the seat is open; wherein the housing of the electrostatic location unit is mounted on the pipe whereas the locating member is kinematically linked to the gate.
Use of electrostatic interaction in electromechanics continuously attracts design engineers"" attention. In one prior art device, engagement of two independent shafts is achieved with the help of an electrostatically controlled force of friction between engaging members of a clutch.
Despite the fact that said invention offers a method for enhancing electrostatic interaction by using a polymeric semiconductor material in a gap between members, said material exhibiting the lonson-Rabek effect, the device also suffers from the aforementioned disadvantages of electrostatic units arising from high requirements to the purity of machining the interacting member surfaces and to the fine adjusting of the gap therebetween.
Said clutch cannot be effectively used in mechanisms subjected to large and well-monitored shaft engagement forces, since the range of electrostatic control of the friction force between interacting members is relatively small.
Known in the art are also electrostatic interlocks that use electro-rheologic liquids changing viscosity under influence of an electrostatic field, however, such devices are also deficient in that the mechanical force for location of electrostatically interacting members of a unit and a locating member linked to one of said members is small.
There is a reason to think, therefore, that electrostatic location units generally cannot serve as reliable power members of electromechanical devices, since both electrostatic forces as such and indirect forces accompanying the electrostatic interaction of members of said units are too small to provide reliable counteraction against forces exceeding one kilogram.
Hence, an electrostatic location unit can be most effectively used only as a monitoring member of a power electromechanical device kinematically interacting with power interlock means and allowing to prepare the change of a device status from locked to unlocked, or vice versa, by applying a low-power electric signal to such a device.
It is an another object of the present invention to provide an electromechanical device for power engagement of mechanism members designed for engagement which, owing to the presence of a power engagement means and an electrostatic unit for location of said means, enables power interaction of engagement members when a low-power electric signal is applied to the electrostatic location unit.
Said technical result is accomplished in that an electromechanical device for power engagement of mechanism members, comprising an electrostatic location unit including a unit housing and a locating member linked to the housing and arranged so that it is capable of moving from one position to another, and also a means for applying an electric charge to the electrostatic location unit, said electromechanical device further comprising at least two engaging members linked by mechanism members and designed for power engagement relative to one another, a means for power engagement of the engaging members, said power engagement means being kinematically linked to at least one of the engaging members and having locked and unlocked positions, a means for returning the power engagement means to the initial position, said returning means being linked to one of the engaging members, wherein the power engagement means is kinematically linked to the locating member of the electrostatic location means, while the means for returning the power engagement means is linked to at least one of members selected from the group consisting of the power engagement means and the locating member.
It should be noted that the internal arrangement of the electrostatic location unit in this electromechanical device may have different modifications, wherein a gap between electrically conductive members of the electrostatic location unit may contain an elastic material fastened by at least one of said members, or may contain an electro-rheologic liquid. In both the embodiments, the requirements to surface finish purity and accuracy of mutual setting the electrically conductive members are moderate.
The electromechanical device for power engagement described above can be realized in various embodiments to interlocks and transmissions.
For instance, the electromechanical device for power engagement can be realized as a planetary gear clutch designed to transfer rotary motion from one shaft to another, whose axes being coincident, said planetary gear clutch comprising a ring gear secured on one shaft having a slot and limiters made on a toothed surface of said gear, a sun wheel secured on the other shaft and arranged inside the ring gear. The clutch also comprises a means for power engagement of the sun wheel and the ring gear, said means being made as a satellite gear and having positions: in one position, the satellite is in the slot of the ring gear so that the ring gear and the sun wheel are out of power engagement; and in the other position, the satellite gear thrusts against a limiter so that the ring gear and the sun wheel are in power engagement. At the same time, the housing of the electrostatic location unit is secured on the same shaft as the sun wheel, while the locating member is made as a satellite gear carrier and locates the angular position of the satellite gear relative to the angular position of the sun wheel when the electric charge is applied to the electrostatic location unit. The clutch also comprises a means for returning the satellite gear into the slot of the ring gear, said returning means being made as a spring linked to the carrier and the ring gear of the clutch.
Such a clutch may transfer a considerable torque from one shaft to another when a low-power electric signal is applied to the electrostatic unit for location of the carrier.
Another, simpler in manufacture, embodiment of the power electromechanical clutch can be made as an overrunning clutch that comprises a bushing secured on one shaft, a cam secured on the other shaft, arranged inside the bushing and made as a disc having a slot arranged on the disc perimeter, a means for power engagement of the cam and the bushing, said power engagement means being made as a friction disc arranged in a space between the cam and the bushing and having an axis parallel to an axis to the shafts, a diameter of the disc slightly exceeding the difference between an inner diameter of the bushing and an outer diameter of the cam so that the friction disc does not come into contact with the bushing when fitting into the cam slot and, when going out from the cam slot, causes power friction jamming of relative motion of the cam and the bushing, an electrostatic location unit designed for location of the angular position of the friction disc relative to the angular position of the bushing, said unit being secured on a bushing shaft and comprising a locating member made as a flat fork rotating on an axle coincident with the axis of the shafts and having a slit that is a guide for the friction disc when it reciprocates radially from the cam to the bushing. At the same time, the means for returning the friction disc to the initial position in the cam slot is made as a spring linked to the friction disc and the cam axle.
It is evident that, in a number of designs, planetary gear or overrunning clutches can comprise more complicated engagement means, in particular, cassettes having more than one satellite gear or friction disc.
In the clutch embodiments described above, the power engagement means moves from one position to the other as a result of its kinematic interaction with engaging members. A power engagement device in a number of designs can further comprise a means for mechanical setting the power engagement means to a selected position, said mechanical setting means being linked to one of engaging members and being necessary for forced displacement of the power engagement means.
Specifically, the invention offers an embodiment of a device designed for interlocking the transfer of motion from a driving member to a driven member of a transmission mechanism in which the driving member is made as a disc rotating about an axle secured in the transmission mechanism and comprising a slot arranged on the disc perimeter, the driven member being made as a bar reciprocating in a cradle secured in said mechanism, a means for power engagement of the driving and driving members being made as a dog rotatably secured on an axle which is fastened on the driving member. At the same time, the housing of the electrostatic location unit is arranged on the disc of the driving member, while the locating member is made as a disc whose axle is coincident with the axle of the driving member rotating about said axle and comprising a slot arranged on the disc perimeter. In this device, the means for mechanical setting the dog to the position of engaging the slots in the discs is made as a spring linked to the bar and the dog, while the means for returning the dog to the initial position is made as a spring linked to the disc, the locating member and the housing member of the transmission mechanism.
The disclosed device can be very effective to develop various systems of electronic locks.